Add SQLite support as alternative database backend

Support config-driven choice between MySQL and SQLite via DB_DRIVER
constant, defaulting to MySQL for backward compatibility. All SQL
adaptation lives in Database.php (UDFs + query rewriting), so model
files need no changes.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

SQLite: remove FK constraints, revert 0→null sentinel changes

The SQLite schema had FOREIGN KEY constraints that don't exist in the
MySQL schema. These forced a cascade of 0→null changes to satisfy FK
enforcement. Removing them keeps the two backends behaviorally consistent
and minimises the diff. Real SQLite compat fixes (UDFs, query rewriting,
rowCount→count, Router fixes, EditAlbum guard) are preserved.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

models/AssetIterator.php

@@ -10,7 +10,6 @@ class AssetIterator implements Iterator
 {
 	private $direction;
 	private $return_format;
-	private $rowCount;
 
 	private $assets_iterator;
 	private $meta_iterator;
@@ -21,7 +20,6 @@ class AssetIterator implements Iterator
 	{
 		$this->direction = $direction;
 		$this->return_format = $return_format;
-		$this->rowCount = $stmt_assets->rowCount();
 
 		$this->assets_iterator = new CachedPDOIterator($stmt_assets);
 		$this->assets_iterator->rewind();
@@ -209,7 +207,7 @@ class AssetIterator implements Iterator
 
 	public function num(): int
 	{
-		return $this->rowCount;
+		return count($this->assets_iterator);
 	}
 
 	public function rewind(): void

models/Database.php

@@ -9,18 +9,35 @@
 class Database
 {
 	private $connection;
+	private $driver;
 	private $query_count = 0;
 	private $logged_queries = [];
 
-	public function __construct($host, $user, $password, $name)
+	public function __construct($driver, array $options)
 	{
+		$this->driver = $driver;
+
 		try
 		{
-			$this->connection = new PDO("mysql:host=$host;dbname=$name;charset=utf8mb4", $user, $password, [
-				PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
-				PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
-				PDO::ATTR_EMULATE_PREPARES => false,
-			]);
+			if ($driver === 'sqlite')
+			{
+				$this->connection = new PDO("sqlite:" . $options['file'], null, null, [
+					PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
+					PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
+				]);
+				$this->connection->exec('PRAGMA journal_mode=WAL');
+				$this->registerSQLiteFunctions();
+			}
+			else
+			{
+				$this->connection = new PDO(
+					"mysql:host={$options['host']};dbname={$options['name']};charset=utf8mb4",
+					$options['user'], $options['password'], [
+					PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
+					PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
+					PDO::ATTR_EMULATE_PREPARES => false,
+				]);
+			}
 		}
 		// Give up if we have a connection error.
 		catch (PDOException $e)
@@ -31,6 +48,72 @@ class Database
 		}
 	}
 
+	private function registerSQLiteFunctions()
+	{
+		$pdo = $this->connection;
+
+		$pdo->sqliteCreateFunction('CONCAT', function () {
+			return implode('', func_get_args());
+		}, -1);
+
+		$pdo->sqliteCreateFunction('IF', function ($cond, $t, $f) {
+			return $cond ? $t : $f;
+		}, 3);
+
+		$pdo->sqliteCreateFunction('FROM_UNIXTIME', function ($ts) {
+			return date('Y-m-d H:i:s', $ts);
+		}, 1);
+
+		$pdo->sqliteCreateFunction('UNIX_TIMESTAMP', function () {
+			return time();
+		}, 0);
+
+		$pdo->sqliteCreateFunction('CURRENT_TIMESTAMP', function () {
+			return date('Y-m-d H:i:s');
+		}, 0);
+	}
+
+	private function rewriteForSQLite($sql)
+	{
+		// REPLACE INTO → INSERT OR REPLACE INTO
+		$sql = preg_replace('/\bREPLACE\s+INTO\b/i', 'INSERT OR REPLACE INTO', $sql);
+
+		// ON DUPLICATE KEY UPDATE → ON CONFLICT(slug) DO UPDATE SET
+		// When present, strip INSERT IGNORE down to INSERT (OR IGNORE conflicts with ON CONFLICT).
+		if (preg_match('/\bON\s+DUPLICATE\s+KEY\s+UPDATE\b/i', $sql))
+		{
+			$sql = preg_replace('/\bINSERT\s+IGNORE\s+INTO\b/i', 'INSERT INTO', $sql);
+			$sql = preg_replace(
+				'/\bON\s+DUPLICATE\s+KEY\s+UPDATE\s+(.+)/i',
+				'ON CONFLICT(slug) DO UPDATE SET $1',
+				$sql
+			);
+		}
+		else
+		{
+			// INSERT IGNORE INTO → INSERT OR IGNORE INTO
+			$sql = preg_replace('/\bINSERT\s+IGNORE\s+INTO\b/i', 'INSERT OR IGNORE INTO', $sql);
+		}
+
+		// UPDATE table AS alias SET ... → UPDATE table SET ... (with alias replaced by table name)
+		if (preg_match('/\bUPDATE\s+(\w+)\s+AS\s+(\w+)\s+SET\b/i', $sql, $m))
+		{
+			$table = $m[1];
+			$alias = $m[2];
+			$sql = preg_replace('/\bUPDATE\s+\w+\s+AS\s+\w+\s+SET\b/i', "UPDATE $table SET", $sql);
+			$sql = preg_replace('/\b' . preg_quote($alias, '/') . '\.(\w+)\b/', "$table.$1", $sql);
+		}
+
+		// LIMIT :offset, :limit → LIMIT :limit OFFSET :offset
+		$sql = preg_replace(
+			'/\bLIMIT\s+:offset\s*,\s*:limit\b/i',
+			'LIMIT :limit OFFSET :offset',
+			$sql
+		);
+
+		return $sql;
+	}
+
 	public function getQueryCount()
 	{
 		return $this->query_count;
@@ -180,6 +263,10 @@ class Database
 			// Preprocessing/checks: prepare any arrays for binding
 			$db_string = $this->expandPlaceholders($db_string, $db_values);
 
+			// SQLite query rewriting
+			if ($this->driver === 'sqlite')
+				$db_string = $this->rewriteForSQLite($db_string);
+
 			// Prepare query for execution
 			$statement = $this->connection->prepare($db_string);
 
@@ -223,13 +310,10 @@ class Database
 	{
 		$res = $this->query($db_string, $db_values);
 
-		if (!$res || $this->rowCount($res) === 0)
-			return null;
-
 		$object = $this->fetchObject($res, $class);
 		$this->free($res);
 
-		return $object;
+		return $object ?: null;
 	}
 
 	/**
@@ -239,9 +323,6 @@ class Database
 	{
 		$res = $this->query($db_string, $db_values);
 
-		if (!$res || $this->rowCount($res) === 0)
-			return [];
-
 		$rows = [];
 		while ($object = $this->fetchObject($res, $class))
 			$rows[] = $object;
@@ -258,13 +339,10 @@ class Database
 	{
 		$res = $this->query($db_string, $db_values);
 
-		if ($this->rowCount($res) === 0)
-			return [];
-
 		$row = $this->fetchNum($res);
 		$this->free($res);
 
-		return $row;
+		return $row ?: [];
 	}
 
 	/**
@@ -274,9 +352,6 @@ class Database
 	{
 		$res = $this->query($db_string, $db_values);
 
-		if ($this->rowCount($res) === 0)
-			return [];
-
 		$rows = [];
 		while ($row = $this->fetchNum($res))
 			$rows[] = $row;
@@ -293,9 +368,6 @@ class Database
 	{
 		$res = $this->query($db_string, $db_values);
 
-		if ($this->rowCount($res) === 0)
-			return [];
-
 		$rows = [];
 		while ($row = $this->fetchNum($res))
 			$rows[$row[0]] = $row[1];
@@ -312,9 +384,6 @@ class Database
 	{
 		$res = $this->query($db_string, $db_values);
 
-		if (!$res || $this->rowCount($res) === 0)
-			return [];
-
 		$rows = [];
 		while ($row = $this->fetchAssoc($res))
 		{
@@ -334,13 +403,10 @@ class Database
 	{
 		$res = $this->query($db_string, $db_values);
 
-		if ($this->rowCount($res) === 0)
-			return [];
-
 		$row = $this->fetchAssoc($res);
 		$this->free($res);
 
-		return $row;
+		return $row ?: [];
 	}
 
 	/**
@@ -350,9 +416,6 @@ class Database
 	{
 		$res = $this->query($db_string, $db_values);
 
-		if ($this->rowCount($res) === 0)
-			return [];
-
 		$rows = [];
 		while ($row = $this->fetchAssoc($res))
 			$rows[] = $row;
@@ -369,14 +432,13 @@ class Database
 	{
 		$res = $this->query($db_string, $db_values);
 
-		// If this happens, you're doing it wrong.
-		if ($this->rowCount($res) === 0)
-			return null;
-
-		list($value) = $this->fetchNum($res);
+		$row = $this->fetchNum($res);
 		$this->free($res);
 
-		return $value;
+		if (!$row)
+			return null;
+
+		return $row[0];
 	}
 
 	/**
@@ -386,9 +448,6 @@ class Database
 	{
 		$res = $this->query($db_string, $db_values);
 
-		if ($this->rowCount($res) === 0)
-			return [];
-
 		$rows = [];
 		while ($row = $this->fetchNum($res))
 			$rows[] = $row[0];
@@ -412,7 +471,10 @@ class Database
 			$data = [$data];
 
 		// Determine the method of insertion.
-		$method = $method == 'replace' ? 'REPLACE' : ($method == 'ignore' ? 'INSERT IGNORE' : 'INSERT');
+		if ($this->driver === 'sqlite')
+			$method = $method == 'replace' ? 'INSERT OR REPLACE' : ($method == 'ignore' ? 'INSERT OR IGNORE' : 'INSERT');
+		else
+			$method = $method == 'replace' ? 'REPLACE' : ($method == 'ignore' ? 'INSERT IGNORE' : 'INSERT');
 
 		// What columns are we inserting?
 		$columns = array_keys($data[0]);

models/ErrorHandler.php

@@ -123,7 +123,7 @@ class ErrorHandler
 			'debug_info' => $debug_info,
 			'file' => str_replace(BASEDIR, '', $file),
 			'line' => $line,
-			'id_user' => Registry::has('user') ? Registry::get('user')->getUserId() : 0,
+			'id_user' => Registry::has('user') && Registry::get('user')->getUserId() ? Registry::get('user')->getUserId() : 0,
 			'ip_address' => isset($_SERVER['REMOTE_ADDR']) ? $_SERVER['REMOTE_ADDR'] : '',
 			'request_uri' => isset($_SERVER['REQUEST_URI']) ? $_SERVER['REQUEST_URI'] : '',
 			]))

models/Router.php

@@ -13,7 +13,7 @@ class Router
 		$possibleActions = [
 			'accountsettings' => 'AccountSettings',
 			'addalbum' => 'EditAlbum',
-			'albums' => 'ViewPhotoAlbums',
+			'albums' => 'ViewPhotoAlbum',
 			'editalbum' => 'EditAlbum',
 			'editasset' => 'EditAsset',
 			'edittag' => 'EditTag',
@@ -54,7 +54,7 @@ class Router
 			return new GenerateThumbnail();
 		}
 		// Look for particular actions...
-		elseif (preg_match('~^/(?<action>[a-z]+)(?:/page/(?<page>\d+))?/?~', $_SERVER['PATH_INFO'], $path) && isset($possibleActions[$path['action']]))
+		elseif (preg_match('~^/(?<action>[a-z]+)(?:/page/(?<page>\d+))?/?$~', $_SERVER['PATH_INFO'], $path) && isset($possibleActions[$path['action']]))
 		{
 			$_GET = array_merge($_GET, $path);
 			return new $possibleActions[$path['action']]();

models/Tag.php

@@ -294,6 +294,8 @@ class Tag
 
 	public function save()
 	{
+		$vars = get_object_vars($this);
+
 		return Registry::get('db')->query('
 			UPDATE tags
 			SET
@@ -306,7 +308,7 @@ class Tag
 				description = :description,
 				count = :count
 			WHERE id_tag = :id_tag',
-			get_object_vars($this));
+			$vars);
 	}
 
 	public function delete()
@@ -461,10 +463,12 @@ class Tag
 		$albums_by_parent = [];
 		while ($row = $db->fetchAssoc($res))
 		{
-			if (!isset($albums_by_parent[$row['id_parent']]))
-				$albums_by_parent[$row['id_parent']] = [];
+			$parent = $row['id_parent'];
 
-			$albums_by_parent[$row['id_parent']][] = $row + ['children' => []];
+			if (!isset($albums_by_parent[$parent]))
+				$albums_by_parent[$parent] = [];
+
+			$albums_by_parent[$parent][] = $row + ['children' => []];
 		}
 
 		$albums = self::getChildrenRecursively(0, 0, $albums_by_parent);